The influence of temperature on the measurements of Reynolds stresses in shear free turbulence near a wall |
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Authors: | L Löfdahl B Johansson C Andersson |
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Institution: | Thermo and Fluid Dynamics, Chalmers University of Technology S-412 96 G?teborg, Sweden, SE
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Abstract: | Temperature changes have a significant influence on the measurements of Reynolds stresses in turbulent boundary layers. As
compared to the spanwise velocity fluctuations the streamwise turbulence intensity is especially sensitive to temperature
deviations. Although this is a general statement its importance is clearly elucidated in a shear-free turbulence near a solid
wall, since the mixing due to turbulence production is minimized in this flow. A consequence of temperature influence on hot-wire
measurements is that frictional heating from the wall has produced contradictory results in different experiments on shear-free
turbulence. In the current paper, measurements of streamwise and spanwise turbulence intensities have been conducted at different
wall temperatures, thereby simulating the contradictory results mentioned above. A simple model has been developed showing
that the turbulence intensities are affected by both the rms. value of the temperature fluctuations and the correlation between
fluctuating temperature and velocity. These correlations are measured and the developed model is used to explain deviations
in earlier measurements on shear-free turbulence. Moreover, the individual magnitudes of the two correlations in the temperature
correction are estimated and their individual importance is discussed.
Received: 17 February 1997 / Accepted: 18 January 1998 |
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